The invention relates to golf clubs. More particularly, the invention relates to golf clubs having an internal brace that effects the United States Golf Association (“USGA”) coefficient of restitution (“COR”) conformity of a wood-type golf club.
A golf club head typically has a face plate that deforms when the face plate strikes the ball. Behaving like a spring, the face plate rebounds to give the ball a higher launch velocity, which is known as the “trampoline effect.” Higher face plate deflection can be realized by using a thin face plate with materials that have low rigidity and high strength. Materials that have these properties include titanium, stainless steel and steel alloys and glass or graphite reinforced composite materials.
The rules of golf, established and interpreted by the USGA and The Royal and Ancient Golf Club of Saint Andrews, set forth certain requirements for a golf club head to limit the “trampoline effect.” Although the rules of golf do not expressly state specific parameters for a golf club face, the rules prohibit the face from having the effect at impact of a spring with a golf ball. The USGA has adopted a test procedure that measures club face COR. This USGA test procedure, as well as procedures like it, may be used to measure club face COR.
A golf club's COR is determined by the following equation:e=(v2−v1)/(U1−U2)where U1 is the club head velocity prior to impact; U2 is the golf ball velocity prior to impact which is zero; v1 is the club head velocity just after separation of the golf ball from the face of the club head; v2 is the golf ball velocity just after separation of the golf ball from the face of the club head; and e is the coefficient of restitution (“COR”) between the golf ball and the club face. The COR limit is at 0.830 for clubs with less than 15 degree loft for all play in the United States and its territories, therefore, scores may be posted for handicap purposes only when achieved with clubs that satisfy the 0.830 COR limit.
Clubs in the art have limited the deflection of the face plate, thus trying to limit the club's COR, by placing a brace plate behind the face plate. This brace plate is attached to the body of the club head. The face plate deflects until it contacts the brace plate, which physically limits the amount of deflection of the face plate, similar to the bottoming out of a trampoline. These clubs require more material and weight to retard face plate deflection.
Other known devices include attached magnets behind the face plate with nut and bolt assemblies. These devices do not effectively stiffen the face plate and are unnecessarily heavy, upsetting the center of gravity location of the club head.